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Show Profile  mcroxford Posted: 22 June 2012, 11:53 AM

Show Profile  Jason Posted: 4 July 2012, 8:41 AM  
The Swedish package for field surveying to CAD with gps claims to provide sub-meter positional precision:
The handset appears to be a convenient form, rugged build and grunty platform for this purpose.
I see the system utilises differential GPS feed to do this. Although real-time dGPS is available in NZ it may not be of the right format for this package?
Has anyone tested the dGPS function of System Asmund in NZ?
What is the PC Mapper proprietary software like to use?

Show Profile  Michael Posted: 2 November 2012, 12:50 AM  
Slightly related to Jason's last post, I got all excited when I found out about (thanks Steve Pyatt). This appears to offer a time series of "corrections" which could be applied (when back home) to the data from a hand-held GPS to improve its accuracy. But a bit of googling dampened my enthusiasm a bit. Seems that the errors as seen by the fixed GPSs may be quite different from the errors in my hand-held, due to different set of satellites each may be using at each instant. Anyone got any experience with this? If its not usable in this way, I wonder why was the PositioNZ network set up?

Show Profile  mcroxford Posted: 5 November 2012, 8:27 AM  
First event (I think) on a Pullautin map. What's that? It is a computer generated map using Lidar data and some other sources in Finland. To be used for Ski-O I think from the poor translation from Google. Check out the size of the map! I'm assuming a 1:10,000?

Show Profile  rossmaxmo Posted: 5 November 2012, 10:01 AM  
Cool eh?? It's actually being for an ultralong distance race called 'Sadismi' - I'm sure you can guess what it means. The map is generated by software created by the dude from Routegadget from an xyz file, at the moment it can give pretty good enough maps for training, with pretty accurate contours, cliffs, rocks and even knolls and vegetation. There's a video by Jan Kocbach running on one of the generated maps here:

You can get the software here:

Show Profile  rossmaxmo Posted: 5 November 2012, 10:02 AM  
*being made for an ultra-long (foot orienteering)

Show Profile  mcroxford Posted: 5 November 2012, 11:44 AM  
If anyone is tempted at some stage I have a Lidar file for the start of Farewell Spit at the very top of the South Island. I may be able to get sufficient info together from my work to put through the programme.

Show Profile  Michael Posted: 5 November 2012, 11:57 AM  
Michael never mind Farewell Spit, can you get Lidar for the top of the Takaka Hill?

Show Profile  mcroxford Posted: 5 November 2012, 12:23 PM  
No! Not yet. My evil plan of infiltrating the decision making part of the GIS team at my Council is yet to work. Actually, they are doing a fly of all the major rivers with Lidar and I am going to try to convince them to send the plane over Canaan on the way to Golden Bay and hopefully do the Howard Valley near St Arnaud.

On the other hand, have you been to the base of Farewell Spit? I will get a map of there one day. It is a mixture of sand dunes, native forest and strangely shaped hills.

Show Profile  Martin Posted: 5 November 2012, 12:49 PM  
I've been playing around with pullautin and it's pretty powerful.

In Auckland the rural tiles don't have a very high density of lidar points. I also didn't have the above ground points for this sample of the Kohekohe map, so some of the finer contour detail hasn't come through.

Another map in progress...

Show Profile  mcroxford Posted: 5 November 2012, 9:00 PM  
Behold. The Holy Grail. Sorry Michael, couldn't help myself. :-)

Show Profile  Michael Posted: 6 November 2012, 4:31 AM  
Fascinating! I suppose the inference of non-contour features might have been calibrated on Scandinavian (?) terrain, how well do you think it's detecting NZ features? Nice to see the absence of U depressions given how few are really 1m deep, but I wonder if the knoll-detector isn't a tad over-sensitive. Would be great to assess these in the field (no doubt you have...)

Show Profile  Martin Posted: 6 November 2012, 4:40 AM  
The dot knoll and small depressions haven't come out particularly well in the Kohekohe example. I think that is because of the low density of the points. The auckland data is 1 point per 25 square meters for rural data and 1 point per 2 square meters for urban data. In comparison the data that the is being used for development is up to 6 points per meter square.

The patch of detail in the trees also didn't show up much. This was probably because I didn't have the above ground points.

So essentially the output is only as good as the input data.

Show Profile  Martin Posted: 6 November 2012, 4:42 AM  
Looking at the Quarry sample, it's picking up areas of vegetation but some very nice white forest is showing up green. At a guess because it has a denser canopy?! The levels of green can be tweaked so that's the next step

Show Profile  Selwyn Posted: 16 November 2012, 4:29 AM  
I have encountered a peculiar issue with saving a map from OCAD11 to OCAD9. Any suggestions welcome.

I create a new map in OCAD11 (or OCAD10), no map symbols yet, set NZTM coordinates for the middle of the proposed map.

From Auckland Council GIS web site download a number of georeferenced orthophoto tiles. In this case four rural tiles because the map sits at the corners of all four. I also have several much smaller urban map tiles that are at high definition and overlap the large rural map tiles in the middle.
The downloads arrive as jpg files each with a jgw file included.

In OCAD11 the map tiles all drop into place delightfully georeferenced. I make all the background images invisible.
I now save the map as OCAD9 with a new file name.

Now using OCAD9, I can open and make visible 2 of the large rural map tiles and all 5 of the small urban map tiles and they all open georeferenced.
But when I try make visible a third background map tile I get error message:
"Internal error: BackgroundMapOption.LoadBackgroundMap"
or sometimes with repeated attempts I get the message "Cannot open (...file path and name)" then the above message.

The implication is this an issue with the size the map.
When all background maps are open the paper size is no bigger than horizontal 1425mm, vertical 1700mm.
My understanding is that Standard versions of OCAD 9,10,11 all allow a paper map size of 4000mm x 4000mm. Or am I wrong?

I tried deleting the jgw files in OCAD11 after opening the background map and it happily retains the georeferencing meaning OCAD doesn't need the jgw files again - a once only positioning is all that's required. This also works when saved back as OCAD9 apart from the error as mentioned above.

Another complication is that if a have both OCAD9 and OCAD11 running, the corruption error that occurs in OCAD9 then repeats in OCAD11. I close OCAD9 and OCAD11 recovers, now able to display all the background images.

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